On some of the local news stations where they interviewed people, several said that they heard a high pitched roar/whine right before the explosion, that's why it was initially reported as a possible plane crash !

Quoting: Anonymous Coward 24599086

If the sound was like a plane revving up, or taking off, that is the same sound that has been heard in Louisiana and Florida. Those who say they know, say that is the sound of pressure releasing from a pipe, i.e. like a steam pipe, or a gas pipe under pressure. It sounds revved up until the pressure levels off (breaks) then winds down.